How to include duplicate keys in HashMap? [duplicate]

Answer 1

Use Map>:

Map> map = new LinkedHashMap< Integer, List>();

map.put(-1505711364, new ArrayList<>(Arrays.asList("4")));
map.put(294357273, new ArrayList<>(Arrays.asList("15", "71")));
//...

To add a new key/value pair in this map:

public void add(Integer key, String newValue) {
    List currentValue = map.get(key);
    if (currentValue == null) {
        currentValue = new ArrayList();
        map.put(key, currentValue);
    }
    currentValue.add(newValue);
}